This clinical research proposal describes a study to evaluate the efficacy and safety of Biphosphonate Therapy for Osteogenesis Imperfecta (OI). OI is a heritable disorder of collagen synthesis. Affected persons have low bone mineral density and experience multiple fractures and progressive bony deformity. In its most severe form, the disorder is lethal in infancy. To date, no effective therapy exists for this debilitating condition. Improvements in bone mineral density and in fracture rates in a small number of children treated with intravenous biphosphonates have been reported. The efficacy of oral biphosphonates has not been established. We will characterize the changed effected by oral biphosphonate therapy and compare them to a regimen of intravenous biphosphonate therapy in a group of children with OI.